Judging from poor sales of mirrorless cameras which are at this point essentially high priced niche cameras, I'd say you are asking the wrong question.

Big, bright, Pentaprism VFs will cease to exist when something comes along that improves viewfinders. That has not happened at all with EVFs, so vendors are still making pentaprism finders. Like an Analogue Synthesizer, the Moog, for example, or the Stradivarius violin, some items were never improved by modern technologies, so they are still made and highly coveted. Judging by the huge number of pros and advanced amateurs who prefer OVFs, the Pentaprism finder may be one such item.